传热学英文版Chap5.pdfVIP

Chapter 5 Principles of Convection 5-1 Introduction Convection: heat transfer between a surface and a flowing fluid. Newton’s law of cooling: q = hA∆T Where h is the convection heat transfer coefficient. Target of study: the way of predicting the value of h. There are different kinds of convection: Forced convection 强制对流 (Flow due to external force) Free convection Without phase change 自然对流 无相变 (Flow due to density difference Mixed convection Convection 混合对流 Boiling 沸腾 With phase change 有相变 Condensation 凝结 h and the temperature field There is no-slip (无滑移) requirement for viscous fluid (粘性流体) flowing over a wall, that is the velocity at the u The Fourier’s Low is applicable: ∝ y q ∂T q −k A ∂y y 0 x k is the heat conductivity of the fluid; ∂T is the temperature gradient in the fluid at the ∂y y 0 position of the wall; as k ∂T q h∆T h − ∆T ∂y y 0 This is an important relation between h and the temperature field in the fluid. 5-2 Viscous (粘性) Flow The region of fl